Recent increases in public concern for the environment have resulted in various government imposed environmental regulations. Among such regulations are requirements relating to the monitoring of groundwater quality. In response to these requirements, water quality analytic capabilities have been improved and water sampling equipment has been developed. Increased monitoring and sampling of groundwater and environmental quality has resulted in a substantial increase in the number of identified sites of contaminated groundwater. Along with the identification of an increased number of contaminated sites has been an increased effort to clean up these sites. This effort at cleaning of contaminated groundwater has lead to a need for improved below ground pumping systems to assist in these clean up efforts.
Once it has been determined that groundwater is contaminated, the clean up effort will often include decontamination of the groundwater by pumping the contaminant from the well. This is feasible where, for example, the contaminant is a floating layer lying above the groundwater. By selectively pumping the contaminant from the groundwater the site may be thereby decontaminated. An added benefit and incentive to pumping groundwater contaminants, such as hydrocarbons, is that the pumped contaminants may be recycled for reuse. Much of the previously developed floating layer equipment has not been effective, however, in permitting the efficient pumping of the floating layer to the exclusion of the groundwater.
It is common to employ what is known as a dual pump system to recover contaminants that are floating on the water within a well. The dual pump system uses a lower pump submerged in the groundwater to create a draw-down in the recovery well by the action of its pumping. This draw-down extends out away from the well and forms what is known as a "cone of depression". The cone of depression defines an area around and away from the recovery well where the natural static water level is lowered, or depressed and the contaminant is induced to flow toward and collect in the recovery well. A second, upper or product pump is then used to pump the contaminant. In this way, the contaminant is collected at a higher rate than by pumping the contaminant alone. In the preferred embodiment, the lower pump removes pure groundwater and the upper pump removes pure contaminant.
Many different types of pumps have been used for both the lower draw-down pump and the upper contaminant pump. For lower recovery wells it is common to use the various types of pneumatic pumps for both functions. When using pneumatic pumps for both the upper and lower pumps, the question of control of the pumps and the coordination of the two pumps working together has always been a costly and complex problem. Whether used for the upper or lower pump, pneumatic pumps are normally under the control of a surface located pneumatic control unit. While the surface located control unit has been used successfully for these types of pumps, there are additional costs and complexity which are added to the cost of the pump itself. When attempting to control two pumps and coordinate the pumping action of both pumps, there is an additional increase in both the cost and complexity of the total system. The cost and complexity can be somewhat reduced by using the pumps which avoid the necessity of external controllers by incorporating sensing means within the pump to detect when fluid has entered the pump to a desired level. Unfortunately, the use of these type of pumps alone does not solve the linking of the two pumps to operate as a total system.
Accordingly, what is needed is a dual pump system which reduces both the cost and complexity of controlling the total pumping system when the two pumps are working together to remove a floating layer of contaminants.
Additional objects, advantages and features of the present invention will become apparent from the following description and appended claims taken in conjunction with the accompanying drawings.